Hawkes said climate change may have set things in motion by affecting food supplies. Savannahs started replacing forests in Africa.
“One of the things it did was restrict the availability of the kinds of things that little kids, little apes, can feed themselves on. So that meant that ancestral moms had two choices. They could either follow the retreating forests, or if they stayed in those environments, then they just would have to feed their kids themselves. The kids couldn’t do it,” she said.
So, if mothers decided to feed their offspring themselves they would not be able to give birth as often. They’d just be too busy finding food. Here’s where granny primate steps in to help.
She said, “It would also mean that older females, whose fertility was coming to an end, could now make a big difference in their fitness by helping their daughters feed those grandchildren. And that would mean that moms could wean earlier.”
The act of early babysitting had long-range effects.
“That whole array of changes could account for why we have longer adult lifespans. We age more slowly. We mature later. Our kids are actually dependent longer, but we wean them earlier than the other apes do. And that hypothesis has been on the table for a while,” said Hawkes.
The caring for their daughters’ offspring may have triggered genetic changes that allowed older females to live longer. Those changes were eventually passed down. Computer simulations show that chimps, who reached adulthood at age 13, lived another 15 or 16 years. But humans in developed countries, who reached adulthood at 19, generally lived another 60 years or more.
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25